Antioxidant enzyme activities and malondialdehyde, glutathione and methemoglobin concentrations in channel catfish exposed to DEF and n-butyl mercaptan.

Indicators of free-radical or oxidant-mediated responses were quantified in channel catfish, Ictalurus punctatus, exposed to the organophosphorus herbicide DEF and its metabolite, n-butyl mercaptan (nBM). The activities of the antioxidant enzymes superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase did not vary significantly with toxicant or dose. The concentrations of reduced glutathione (GSH) and malondialdehyde (MDA) did not vary significantly with toxicant or dose. The percentage of methemoglobin increased in the nBM-exposed fish with dose, up to 16.5% of total hemoglobin. The DEF-exposed catfish had no significant increases in methemoglobin compared to controls.